may be solves this error

Traceback (most recent call last):
  File "/home/olli/.virtualenvs/expn/bin/pythontidy", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/home/olli/.virtualenvs/expn/lib/python2.7/site-packages/pkg_resources.py", line 2813, in <module>
    add_activation_listener(lambda dist: dist.activate())
  File "/home/olli/.virtualenvs/expn/lib/python2.7/site-packages/pkg_resources.py", line 686, in subscribe
    callback(dist)
  File "/home/olli/.virtualenvs/expn/lib/python2.7/site-packages/pkg_resources.py", line 2813, in <lambda>
    add_activation_listener(lambda dist: dist.activate())
  File "/home/olli/.virtualenvs/expn/lib/python2.7/site-packages/pkg_resources.py", line 2346, in activate
    list(map(declare_namespace, self._get_metadata('namespace_packages.txt')))
  File "/home/olli/.virtualenvs/expn/lib/python2.7/site-packages/pkg_resources.py", line 1930, in declare_namespace
    path = sys.modules[parent].__path__
KeyError: 'da'